from django.conf import settings
from django.core.exceptions import PermissionDenied
from django.core.urlresolvers import reverse
from django.contrib.auth.decorators import login_required
from django_future.csrf import ensure_csrf_cookie
from mitxmako.shortcuts import render_to_response

from xmodule.modulestore import Location
from xmodule.modulestore.django import modulestore
from contentstore.utils import get_url_reverse, get_lms_link_for_item
from util.json_request import expect_json
from auth.authz import STAFF_ROLE_NAME, INSTRUCTOR_ROLE_NAME, get_users_in_course_group_by_role
from auth.authz import get_user_by_email, add_user_to_course_group, remove_user_from_course_group

from .access import has_access
from .requests import create_json_response


def user_author_string(user):
    '''Get an author string for commits by this user.  Format:
    first last <email@email.com>.

    If the first and last names are blank, uses the username instead.
    Assumes that the email is not blank.
    '''
    f = user.first_name
    l = user.last_name
    if f == '' and l == '':
        f = user.username
    return '{first} {last} <{email}>'.format(first=f,
                                             last=l,
                                             email=user.email)


@login_required
@ensure_csrf_cookie
def index(request):
    """
    List all courses available to the logged in user
    """
    courses = modulestore('direct').get_items(['i4x', None, None, 'course', None])

    # filter out courses that we don't have access too
    def course_filter(course):
        return (has_access(request.user, course.location)
                and course.location.course != 'templates'
                and course.location.org != ''
                and course.location.course != ''
                and course.location.name != '')
    courses = filter(course_filter, courses)

    return render_to_response('index.html', {
        'new_course_template': Location('i4x', 'edx', 'templates', 'course', 'Empty'),
        'courses': [(course.display_name,
                    get_url_reverse('CourseOutline', course),
                    get_lms_link_for_item(course.location, course_id=course.location.course_id))
                    for course in courses],
        'user': request.user,
        'disable_course_creation': settings.MITX_FEATURES.get('DISABLE_COURSE_CREATION', False) and not request.user.is_staff
    })


@login_required
@ensure_csrf_cookie
def manage_users(request, location):
    '''
    This view will return all CMS users who are editors for the specified course
    '''
    # check that logged in user has permissions to this item
    if not has_access(request.user, location, role=INSTRUCTOR_ROLE_NAME) and not has_access(request.user, location, role=STAFF_ROLE_NAME):
        raise PermissionDenied()

    course_module = modulestore().get_item(location)

    return render_to_response('manage_users.html', {
        'active_tab': 'users',
        'context_course': course_module,
        'staff': get_users_in_course_group_by_role(location, STAFF_ROLE_NAME),
        'add_user_postback_url': reverse('add_user', args=[location]).rstrip('/'),
        'remove_user_postback_url': reverse('remove_user', args=[location]).rstrip('/'),
        'allow_actions': has_access(request.user, location, role=INSTRUCTOR_ROLE_NAME),
        'request_user_id': request.user.id
    })


@expect_json
@login_required
@ensure_csrf_cookie
def add_user(request, location):
    '''
    This POST-back view will add a user - specified by email - to the list of editors for
    the specified course
    '''
    email = request.POST["email"]

    if email == '':
        return create_json_response('Please specify an email address.')

    # check that logged in user has admin permissions to this course
    if not has_access(request.user, location, role=INSTRUCTOR_ROLE_NAME):
        raise PermissionDenied()

    user = get_user_by_email(email)

    # user doesn't exist?!? Return error.
    if user is None:
        return create_json_response('Could not find user by email address \'{0}\'.'.format(email))

    # user exists, but hasn't activated account?!?
    if not user.is_active:
        return create_json_response('User {0} has registered but has not yet activated his/her account.'.format(email))

    # ok, we're cool to add to the course group
    add_user_to_course_group(request.user, user, location, STAFF_ROLE_NAME)

    return create_json_response()


@expect_json
@login_required
@ensure_csrf_cookie
def remove_user(request, location):
    '''
    This POST-back view will remove a user - specified by email - from the list of editors for
    the specified course
    '''

    email = request.POST["email"]

    # check that logged in user has admin permissions on this course
    if not has_access(request.user, location, role=INSTRUCTOR_ROLE_NAME):
        raise PermissionDenied()

    user = get_user_by_email(email)
    if user is None:
        return create_json_response('Could not find user by email address \'{0}\'.'.format(email))

    # make sure we're not removing ourselves
    if user.id == request.user.id:
        raise PermissionDenied()

    remove_user_from_course_group(request.user, user, location, STAFF_ROLE_NAME)

    return create_json_response()